1. Field of the Invention
The present invention relates to a semiconductor light-emitting device using a compound semiconductor material and, more particularly, to a semiconductor light-emitting element, e.g., a semiconductor laser, having a sufficiently large band gap between an active layer and a cladding layer.
2. Description of the Related Art
Recently, development in semiconductor lasers has been aimed at an application of an optical information processing optical source, e.g., an optical disk system and a high-speed laser printer. Especially, a GaAlAs-based semiconductor laser in which an active layer is constituted by GaAs and a cladding layer is constituted by GaAlAs and which has an oscillation wavelength in a 0.8 .mu.m wavelength band is under development as a promising semiconductor laser. Some of such semiconductor lasers already have high reliability and have been put into practical use.
However, the GaAlAs-based semiconductor laser does not necessarily have sufficiently good temperature characteristics when it is used in an automobile, or operated in a severe atmosphere or with a high output. For this reason, limitations such as use at a temperature of 100.degree. C. or less are imposed.
In order to solve these problems, it is effective to increase the band gap difference between the active and cladding layers. For example, the Al atomic ratio x of Ga.sub.1-x Al.sub.x As, which is usually 0.4, is increased to 0.8 or more. However, problems still arise such that impurity doping becomes difficult, or transition contributing to electric conduction becomes indirect X transition having a small band gap change with respect to the Al atomic ratio. Hence, the Al atomic ratio cannot be increased.
In this manner, in the conventional GaAlAs-based semiconductor laser, the band gap difference between the active and cladding layers cannot be sufficiently increased, and the semiconductor laser is limited to the operation at a temperature of 100.degree. C. or less.